Objective  Infrared thermal imaging technology has irreplaceable application value in the current national defense and military field. It is the key component of infrared warning, search and tracking, precision guidance and other modern all-weather war applications. In order to meet the compatibility requirements of various high-performance photoelectric weapon platforms, the lightweight, miniaturization and low-cost of infrared optical systems have become important indicators for the comprehensive performance evaluation of new-generation infrared imaging systems. To realize the fabrication of a new generation of thin and light infrared optical system, it is urgent to develop a new type of manufacturable infrared optical materials, striving to provide more material choices and more freedom of design for the design of infrared optical system. For this purpose, the new generation of infrared imaging optical system based on novel chalcogenide glasses is designed here.

  Methods  Three new typical optical systems based on novel chalcogenide glass materials are developed in this paper. We have exploited novel chalcogenide glass materials by taking full advantage of the special characteristics of modifiable glass components and tunable dispersion parameters. Using the high refractive index chalcogenide glass NBL-TQIR-1, whose refractive index is 3.18, the small-sized germanium-free design of the mid-wave infrared (MWIR) imaging optical system can be effectively realized (Fig.2). To match the uncooled mid/short-wave infrared (MW/SWIR) confocal plane infrared detector, the lightweight common path optical system is designed utilizing the novel stacked gradient refractive index (GRIN) sulfide glass lens with different refractive index difference Δn=0.25 (Fig.3). To match the cooled medium/long-wave infrared (MW/LWIR) confocal plane infrared detector, the compact common path optical system is designed utilizing the novel GRIN sulfide glass lens with different refractive index difference Δn=0.3 (Fig.4). Under the requirements of the same system index, the performance of infrared optical systems based on traditional infrared materials and novel chalcogenide glass is compared respectively (Tab.4-Tab.6).

  Results and Discussions   Based on the novel high refractive index chalcogenide glass NBL-TQIR-1 lens, the small-sized non-germanium MWIR double-fields optical imaging system is designed. The results of CODEV simulated analysis show that the performance of this NBL-TQIR-1 optical system is better than that of the traditional infrared materials. At the same time, the new optical system has two fewer lenses and one less aspheric surface than the traditional crystal optical system, the weight of the optical system is reduced by 35%, the length of the optical system is reduced by 15%, and the transmittance is increased by 10%. Based on the novel Δn=0.25 GRIN sulfide glass lens, the lightweight common path MW/SWIR confocal optical system is designed. The results of CODEV simulated analysis show that the novel dual-band NBL-GRIN MW/SWIR optical system is designed using only two new sulfide lenses, two fewer lenses and one fewer aspheric surface than the traditional materials optical system, and the removal of diffraction surfaces. Under the same performance requirements, the weight of the new optical system is reduced by 40%, the length of the system is reduced by 30%, and the transmittal rate is increased by 15%. The optical transfer function MTF (@ characteristic frequency 42 lp/mm) of the former is 10% higher than that of the latter. Based on the novel Δn=0.3 GRIN sulfide glass lens, the compact common path MW/LWIR confocal optical system is designed. The results of CODEV simulated analysis show that the novel dual-band optical system is designed by using only two lenses, the performance of the NBL-GRIN MW/LWIR optical system is comparable to that of the conventional optical system. However, the total length of the system is reduced by 20%, the weight is reduced by 25%, and the transmittance is increased by 18%. As the NBL-GRIN chalcogenide glass dual-band optical system has two fewer lenses and two fewer aspheres, the fabrication and assembly costs of the new system have been greatly reduced.

  Conclusions  In this study, the novel chalcogenide glasses with high refractive index and gradient refractive index are exploited. High refractive index chalcogenide glass NBL-TQIR-1 can replace germanium lens in MWIR optical system so as to realize the small-sized and low cost design. The GRIN chalcogenide glass with different refractive index difference Δn has excellent chromatic aberration correction ability in the dual-band imaging system, providing rich dispersion options for the miniaturization design of a new generation of confocal dual-band infrared imaging systems. The appearance of novel chalcogenide glass is a beneficial supplement to the existing infrared materials, and provides more material choices and more freedom of design for the new generation of transmissive infrared imaging system.